After 35 years, a new federal standard to strengthen vehicle roofs to protect occupants in rollover crashes is supposed to be published July 1.

Then again, maybe not. It looks like the rule has hit yet another speed bump. Rollover accidents cause more than 10,000 fatalities a year. Yet contention over the strength of the standard and how to properly test roof strength has led safety groups and some members of Congress to urge delay, most recently at a June 4 hearing.

The "roof crush" debate is in the league of the regulatory fight between automakers and safety advocates that preceded the implementation of air bags: long and acrimonious.

"We have been waiting almost 40 years for an upgrade,'' said Jacqueline Gillan, vice president of Advocates for Highway and Auto Safety, a Washington-based nonprofit organization. "What has the agency been doing?"

The National Highway Traffic Safety Administration discussed updating the roof crush rule in 2003, Gillan said. "Now, it's five years later, and they couldn't come up with a better rule than this?"

The current standard requires vehicles to withstand force applied to one side of the roof at 1.5 times the vehicle's unloaded weight. A Clinton administration effort to strengthen the rule in the mid-1990s as part of a broader rollover standard fizzled.

The debate was kept alive by an increase in the number of sport-utility vehicles and pickup trucks on the road and a rise in rollover crashes. The failure of Firestone tires on Ford Explorers that rolled over focused public attention on the issue and prompted calls from Congress for reforms.

Under orders from Congress, NHTSA proposed raising the standard in 2005 to 2.5 times the weight of the vehicle. This year, the agency proposed testing the roof on both sides.

Lawmakers set the July 1 deadline when they told NHTSA to upgrade the standard as part of a comprehensive approach to addressing rollovers.

After factoring in technical improvements to cars, such as better stability control and stronger door locks, the agency concluded in 2005 that increasing roof strength would save 44 lives annually and prevent up to 793 injuries. Costs to the carmakers would be up to $95 million a year.

Many new cars already meet the proposed standard, and safety groups and the insurance industry say the rule should be set at 3 times the weight or higher.

Two recurring themes in the debate have been how to conduct the tests and how strong the connection is between crushed roofs and injuries.

Some safety groups want crash dummies filmed in actual cars being rolled over. Instead, the government uses a steel plate to crush a corner of the vehicle roof.

The Alliance of Automobile Manufacturers says there is no relationship between a stronger roof "and the risk of serious head/neck/face injury for belted occupants," according to testimony by Robert Strassburger, vice president of vehicle safety for the trade group, at the Senate automotive safety subcommittee hearing.

Automakers associate rollover fatalities to such factors as speed, alcohol use, the age of the driver and whether a seatbelt is buckled.

Safety groups say a stronger roof protects all ages and types of drivers. In March, the Insurance Institute for Highway Safety in Washington released a study that found that, in a test of 11 SUVs, "the weaker the roof, the more likely an injury."

"It always seemed illogical to us that roof strength didn't make a difference," said Adrian Lund, president of the insurance industry-funded group, which also does independent front- and side-crash testing of vehicles.

So after nearly four decades, people are suddenly asking, "what's the rush?" They reason regulators need to get the details right because the next update is likely to take 30 more years.

Safety groups are willing to wait for a new administration, saying that the agency's proposal is weak. The auto industry isn't in any hurry either, though for a different reason.

Michael Stanton, president and chief executive of the Association of International Automobile Manufacturers in Washington, which represents carmakers such as Nissan, Suzuki and Kia Motors, said his members will need up to six years to implement any changes in concert with model changes.

"Lead time is huge on this one," he said.

Sen. Mark Pryor (D-Ark.), who chaired the recent hearing, said he wants a stronger rule and for regulators to ask for more time if they need it.

"I hope NHTSA will take safety into consideration and not politics and come up with the best public policy," he said.

An agency official working on the rule said NHTSA will notify Congress if it needs more time.

Sen. Tom Coburn (R-Okla.), who testified at the hearing, said he also has doubts about the proposal.

"I am not for more government, but I am for safety,'' he said. He predicted that if the agency doesn't "do the right thing, Congress will write a rule for them."